Catalysts for the addition polymerization of unsaturated organic compounds



starts.

Patented July-31, 1945 CATALYSTS FOB m ADDITION POLYMER- IZA'I'ION COMPOUNDS wiuim Mm Akron. oi'lis,

Goodrich company, New

B. I. oorporaticnofNewliork Application Serial N0. 87'1".

0F UNSATUIATID ORGANIC adgnorto'lhe' I ch, 8.1.,a

lehrn'ry mini.

1: (mm. 10!. sea-cu) Thisinvention relates to the polymerisation of unsaturated organic com-pounds which are dapable of undergoing an addition polymerisation to form high molecular weight linear polymers,

more particularly to the polymerization oi coniumea butsuienes either alone, in mixtures with one another or with other polymeriaable ccmonomers such as the vinyl and vinylidene coinpounds. The principal obiect oi the invention is I to provide a new class 0! catalysts or accelerators oi polymerisation-by the use or which-improved polymers may be obtained in increased'yield and in a much shorter interval oi time.

,It is known that addition polymerisations may be accelerated or promoted by the 0! glyceril e tetrahydric alcohols such as erythritcl;

pentahydrlc. alcohols such as adonitol, arabitol, xylitol, r'hamnitol and the like; ,hexahydric alcohols such as d-, 1- or dl mannitol, dor l iditol, sorbitol, dulcitol, d-talitol, rhamnohexitcl and the like; the. cycioaliphatic diliy'dl 'ic alcohols of the mlopentane series such as cyclopentane, 1-! die]: the cycloaliphatic di, tri and various substances among which are oxygen and oxygen yielding compounds such as hydrogen peroxide, bennoyl peroxide and per-salts. However, with the .use of such lmown poiyme'riaatim initiators, considerable diiliculty is still experienced in obtaining high yields of a desirable,

polymer in a short interval of time. Particularly in the commercial manui'acture oi polymers by emulsion polymerization. the production schedule is frequently disrupted by slow reactions and ions induction v periods before the polymerization polyhydric alcohols oi the cycle-hexane series such as cyclohexane 1-2 diol; reaorcitol, quinitol, pyrogallitol, phloroglucitol, cyclohexane. 13,8,4 tetrol, quel'citol, inositol', ldambcnitol, pinitol quebrachitol, scyllitol; mytilitol and the Mercycloaliphat'ic dihydric alcohols oi the 'cycloheptane series such as cycloheptane-1-2 diol; cycioaliphatlc polyhydrlc alcohols oi the terpene, menthane or pineneseries such as ,tcrpin, pinol hldrate and the like and other aliphatic compoundscontaining two-or more hydrory groups. Alsoincludedinthieclassoicompoundsare those which contain another-functional group in adciticctothetwccrmoreiiycmxrsrcuossuch I have now discovered a large number of substances which have beentermed redox systems because of their property of catalyzing or promoting oxidation reduction reactions, particularly those occurring in biological processes, which v substances are quite effective in promoting ail-- dition polymerizations and which are vastly superior to any previously described polymerization initiators or accelerators in that the polymerisation is carried out in a much shorter'timqthe induction period is largely eliminated, lower temperatures'ior the polymerization may beemployed and consequently a higher molecular 'weight more linear polymer more duh-able Properties is obtained.

"oses such as fructose or levulose, sorbose The class 01 redca systems' with men the present invention is is that class j which comprises an organic aliphatic pclyhydl'oxy compound aheauy metalialt combined therewith, ilheclass or 'ccmpounds designated as aliphatic compounds, includes those aliphatic organic compounds two or whether of theo'pen chain aliphatic'series or the .closed chair'or i 17. be mcnflilifidfas eaasnpleliot compoimlh-in this ciassthedihydricalcdhcls such roups- Ashereinabcve statedthcse as the aide, keto or amino substituted derivatives oi the pclrhydroxy compounds. Especially important inthis group are the side, and keto derivatives oi. straight chained pclyh rosy compounds or. as they are commonly called, the

susars. Among these arethe aldotrloscs such as sly l'ose: ketotrioses such as dioxyacetone; aldotetroses such as erythrose and threose; ketctetroses such as erythrulose; aldopentosessuch asarabincse, :ryiose, lyxose, and ribose; ketcpentoses such as arabcketose and xyloketcse; aldohexoses such asglucose, galactose, mannose, gulose, idose, talose, allose and the like; ketohra the like; and other sugars including the discochsrides and trisaccharides such as sucrose.

maltose, lactose and ramnose; Other derivatives of ll lyhydrosy compounds includedin this invention are the amino substituted po yhydruxy ccmpcunds such as salactamine,gluoosamine, i'ructose amine aud-thelike.

allilha 9 17 'w mcrisationswheneombinsd with a heavy metal "salt; The metal as is mfint to hichidwmetlllic elements which have a density. than .iour', an atomic weight greaterthaniorty and-a'lowatomic (ratio icmhttodonsityl andsppear sumtinlly'atdihe minimum points'm an atomic weightoiiortyonlothsr'ltevesscurve oratcmicvolume'swifleesnystandardtesthoot a eflwlcna m1; mic-1e aloohclsuch as' allnorsanicchsmistrysuchasmi'aim'q'extbook of Inorganic Chemistry," page 30, or Caven and Lander Systematic Inorganic Chemistry facing page 30.) The term heavy metal" includes, therefore, those metallic elements appearing in the center positions of the long periods of a periodic table arranged in short and long periods, and especially those occurring in the 6th to 12th positions of the long periods (considering the alkali metals to occupy the first position and all the rare earth metals to occupy a single position) that is, the elements occurring in group VIII of the Mendeleef Periodic Table such as iron, cobalt and nickel, those in sub-group B of group I and II of the Mendeleef Periodic Table such as copper, silver, zinc, cadmium and mercury, and those in subgroup A of groups VI and VII of the Mendeleef Periodic Table such as chromium, manganese and molybdenum.

The class of redox systems of this invention is meant to include broadly any of the heavy metals mentioned above when in the form of one of their salts combined with any of the polyhydroxy compounds mentioned above. The metal may be combined with the polyhydroxy compound either as a complex compound of uncertain chemical structure, or combinations or polyhydroxy compounds and heavy metals not known to form complexes may be used. In the latter event the redox system will consist of a mixture of the metal in the form of one of its simple salts together with the polylrvdroxy compounds. The preferred redox systems are those which contain a polyhydroxy compound containing from three to live hydroxy groups, and from four to six carbon atoms or a polyhydroxy compound containing from three to live hydroxy groups, from four to six carbon atoms and another group such as aldo,keto, or amine groups, preferably aldo or keto ro p in combination with the salts of heavy metals occurring in the 6th to 12th positions of the first long period of the periodic table such as iron, cobalt, nickel, copper and manganese, The compounds which occur naturally or are derived from naturally occuning substances such as the sugars, and the naturally occurring cyclitols, in combination with a water soluble heavy metal salt, are particularly preferred. Specifically, the keto hexose sugars such as levulose or sorbose, the aldo hexose sugars such as glucose and the naturally occurring cyclitol, quebrachitol, are especially desirable in the practice of this invention.

In the practice of this invention monomeric compounds or mixtures of monomers are polymerized by well known methods of polymerization such as by polymerization in homogeneous systems or by polymerization in emulsions in presence of catalytic amounts of the redox systems of this invention. In the emulsion polymerization process which is at present preferred, the monomer or monomer mixture is emulsified in a non-solvent liquid, usually water, with the aid dox system does not inhibit or poison the polymerization reaction. For most purposes only catalytic amounts of the redox system, say less than 2% by weight based on the weight of the monomers, are preferred and in most instances the polymerization proceeds most rapidly when from 0.05 to 1% of the redox system. is present. when the polyhydroxy compound and heavy metal are added as separate compounds a mixture of about .5% of the polyhydroxy compound and 0.1% oi the heavy metal salt is preferred. When using some heavy metals, particularly copper and manganese, however, it is desirable to use even smaller concentrations of the heavy metal salt, less than 0.01%, since these metals in higher concentration tend to inhibit the polymerization.

As has been mentioned hereinabove, the redox systems of this invention may be used, generally, in the polymerization of those unsaturated organic compounds which are capable of undergoing an addition polymerization to form a high molecular weight linear polymer. Included in this class of monomers are the conjugated butadienes such as butadiene, isoprene, dimethyl butadiene, chloroprene, plperylene and the like all of which contain a group; monomer mixtures of two or more of these butadienes such as a mixture of butadiene and dimethyl butadiene: and monomer mixtures of one or more of these conjugated butadienes with one or more other compounds which also contain group and copolymerize with conjugated butadienes such as mixtures of butadiene with vinyl compounds including aryl oleflns and substituted 'other vinyl compounds such as vinyl ketones,

' vinyl ethers, vinyl carbazole, vinyl furane and of an emulsifying agent and polymerization is then eflected' by adding the heavy metal, polyhydroxy compound of this invention together, if desired, with various other substances, the nature of which will be described hereinafter, and agitating the emulsion until polymer is formed. 'Ih'e resultin polymerized emulsion containing polymer particles dispersed in a liquid medium greatly resembles natural rubber latex and may be coagulatedintheusualmannertoyieldthesolidpolymer.

Theamountoitheredox systemstobeusedin Polymerization may be varied over rather wide limits provided that an excessive amount of the rethe like. Monomer mixtures of butadienes with other compounds, besides vinyl type compounds,

which also contain a group such as vinylidene chloride and the like may also be used. All these monomers and monomermixtures when polymerized or copolymerized in the manner herein described form high molecular weight linear polymers. When the conjugated butadiene is the monomer or is the predominant constituent of a monomer mixture such polymers arev rubbery in character and may be called synthetic rubber.

Other monomers or monomer mixtures which are capable of undergoing arr-addition polymerization and which may be used in the process of this invention are the above mentioned vinyl and vinylidene compounds as well as other vinyl compounds such as vinyl chloride and vinyl acetate, either alone or in mixtures with one another, all of which polymerize to yield a linear polymer of a thermoplastic resinous character.

pared with various emulsifying agents and containing various other catalysts, initiators, promoters, accelerators or modifiers o1 polymerization. As emulsifying agents, partially neutralized fatty acid soaps such as 70-90% neutralized myristic or palmitic acids are particularly efiectlve but well known emulsifying agents including completely neutralized fatty acid soaps such as sodium oleate and sodium palmitate and hymolal sulfates or sulfonates such as sodium sulfate and sodium isobutyl naphthalene suli'onate may also' with other known polymerization initiators such as diazoaminobenzene, trichloracetic acid ,and carbon tetrachloride. They may also be used advantageously in polymerizations which employ a reducing agent such as sulfur dioxide as the polymerization initiator, or in polymerizations efiected in presence of both an oxidizing and a reducing substance. Moreover the redox systems disclosed herein may be used to eiTect polymerizations carried out in the absence of an added initiator, such polymerizations being incapable of proceeding without the redox system.

They may also be employed in the polymerization of emulsions containing a" polymerization modifier such as the dialkyl dixanthogens, diaryl disulfides, thiuram disulfides and other sulfur containing compounds known to increase the solubility and plasticity of polymers.

Although the exact manner in which the p lyhydroxy compound heavy metal redox systems accelerate polymerization is not known with certainty, it is believed that the redox system promotes or catalyzes an oxidation reduction reao tion which oxidizes or activates the monomer molecules to such an extent that they are then capable of initiating a chain reaction which produces a linear polymer. The redox system may directly catalyze the oxidation of the monomer by an oxidizing agent such as a peroxide, if such is present, or it may be auto-oxidizable, and be capable of inducing monomer oxidation or activation by an oxidation reduction involving the redox system itself, or some other mechanism,

may be responsible for the increase in the rate of polymerization and for the improved properties of the polymerization products. The association of small amounts of heavy metals with various polyhydroxy compounds in biological, systems which undergo oxidation reactions is well known and many theories have been propounded for an explanation of such biological oxidoreductions. Since it is believed that the initiation of polymerization reactions is quite similar to biological oxidation reductions particularly as regards the role of the redox catalyst, analogies of polymerization systems with biological systems have proved of greatvalue in elucidating theacticn of the, redox systems. of this invention. It is to be understood however, that the invention is not to be limited by'any proposed theory'since the inclusion of the substances herein described and herein designated as redox systems in polymerization mixtures greatly accelerate the process and also improves the quality of the polymerization products.

In order to illustrate the practice of this invention and to show the accelerating effect of the redox systems 01' this invention upon polymerization, an emulsion containing the following ingredients is prepared:

Butadiene g 55 Acrylonltrile g 45 Hydrogen peroxide (3%% solution) cc 10 Emulsiiying solution (2% aqueous soln. of

myristic' acid 85% neutralized with NaOH) cc 250 Polymerization modifier g 0.3

(6) .001 by weight of cuprous chloride .05% by weight of levulose ("7) 0.10% by weight of cuprous chloride The emulsions are then placed in sealed glass tubes and rotated at 30 C. At various intervals the percent yield of polymer is determined. The rate of polymerization for the various tubes is shown as follows:

It may be seen that with no redox system added, the polymerization is not started after 12% hours and is not complete until 45 hours; with an iron salt alone, 23 hours are required; while with the redox systems of this invention containing a heavy metal salt and apolyhydrc-xy compound, polymerization is substantially complete after only 12 /2 hours. With a copper salt alone, there is no polymerization even after 45 hours, but with a copper salt levulose redox system polymeriz'ation is substantially complete in 12 hours.

In another embodiment of the invention a monomer mixture containing 25 g. of styrene and 7.5 g. of butadiene is emulsified with 25 cc. of a 2% aqueous sodium myristate solution, and in presence of 0.035 g. of hydrogen peroxide 0.03 g. of a polymerization modifier and .20 g. of sodium pyrophosphate. The emulsion requires 110 hours at only 71 hours at 30 C. to yield 92% of arubberlike copolymer which is considerably more plastic and more soluble in acetone.

Other embodiments of the invention in which various other polyhydroxy compounds'are used with salts of various heavy metals and with various monomer mixtures, initiators and emulsifying agentsal'so show that the polymerization velocity is increased by the practice of this invention. For example it is possible to polymerize a butadiene vinyl-type comonomer mixture using a heavy metal salt and a sugar in a very short time without any initiator other than molecular oxygen, being present. Systems employing a sugar, molecular oxygen and other redox systems which contain a heavy metal salt combined with other compounds including sodium pyrophosphate, levullnic acid, beta-mercapto ethanol and cholesterol such as are disclosed in copending applications of William D. Stewart, Serial Nos. 379,713: 379,714; 379,715 and 379,717 filed Feb. 19, 1941, are also quite effective in promoting polymerizations.

In the practice of the invention it is sometimes desirable to add various substances other than those mentioned above to the polymerization recipe. For example, when employing redox systems which are very efiective in biological processes such as the quebrachitol heavy metal system it may be desirable to add colloids which are present in biological systems as carriers for the redox system, such as proteins, peptides, polypeptides or other colloidal material. It may also be desirable to add materials which influence the quality of the finished polymer such as various plasticizing or stabilizing agents for the polymer.

The practice of this invention also allows polymerization to proceed rapidly under conditions where polymerization would ordinarily be impossible, because the great accelerating efiect of the redox system more than counteracts the inhibiting effect of other substances which would prevent the polymerization. Many such inhibiting substances are difficult to exclude from the polymerization batch because they are present as impurities in the monomers or in other essential materials.

Although various embodiments of the invention have been herein disclosed, it is not intended that the invention be limited solely thereto for it will be obvious to those skilled in the art that many modifications and variations are within the spirit and scope of the invention as defined by the appended claims.

Iclaim:

1. The method which comprises subjecting a monomeric material comprising a polymerizable conjugated butadiene to polymerization in aqueous emulsion in the presence of a catalyst comprising a water-soluble heavy metal salt combined with a sugar, the total concentration of the heavy metal salt and the sugar being less than 2% by weight of the material polymerized and the concentration of the heavy metal salt being such that the polymerization proceeds more rapidly than in the absence of the heavy metal salt.

2. The method of claim 1 wherein the heavy' metal salt is a salt of a heavy metal occurring in group VIII and the first long period of the periodic table.

group and is copolymerizable therewith in aqueous emulsion, to polymerization in aqueous emulsion in the presence of a catalyst comprising a water-soluble heavy metal salt combined with a sugar, the total concentration of the heavy metal salt and the sugar being less than 2% by weight of the material polymerized and the concentration of the heavy metal salt being such that the polymerization proceeds more rapidly than in the absence of the heavy metal salt.

4. The method of claim 3 in which the heavy metal salt is a salt of a heavy metal occurring in the 6th to 12th positions of the first long period of the periodic table.

5. The method of claim 3 in which the heavy metal salt is a salt of a heavy metal occurring in the 6th to 12th positions of the first long period of the periodic table and the sugar is a monosaccharide.

6. The method of claim 3 in which the material polymerized is a mixture of butadiene-1,3 and a copolymerizable vinyl compound; the heavy metal salt is a salt of a heavy metal occurring in the 6th to 12th positions of the first long period of the periodic table; and the sugar is a monosaccharide.

7. The method of claim 3 in which the material polymerized is a mixture of butadiene-1,3 and a copolymerizable vinyl compound; the heavy metal salt is a. salt of a heavy metal occurring in group VIII and the first long period of the periodic table; and the sugar is a ketohexose.

8. The method of claim 3 in which the material polymerized is a mixture of butadiene-1,3 and acrylonitrile and the catalyst comprises levulose and a water-soluble cobalt salt.

9. The method of claim 3 in which the material polymerized is a mixture of butadiene-1,3 and acrylonitrile and the catalyst comprises levulose and a water-soluble iron salt.

10. The method of claim 3 in which the material polymerized is a mixture of butadiene-1,3 and a copolymerizable vinyl compound; the heavy metal salt is a salt of a heavy metal occurring in the 6th to 12th positions of the first long period of the periodic table; and the sugar is an alclohexose.

11. The method of claim 3 in which the material polymerized is a mixture of butadiene-1,3 and acrylonitrile and the catalyst comprises glucose and a water-soluble copper salt.

12. The method which comprises subjecting a polymerizable material comprising an unsaturated organic compound which contains a group and which undergoes in aqueous emulsion an addition polymerization to form a high molecular weight linear polymer, to polymerization in aqueous emulsion in the presence of a catalyst comprising a water-soluble heavy metal salt com bined with a sugar, the total concentration of the heavy metal salt and the sugar being less than 2% by weight of the material polymerized and the concentration of the heavy metal salt being such that the polymerization proceeds more rafiidly than in the absence of the heavy metal sa WILLIAM D. STEWART. 

